Soon after Muslim scholar Tariq Ramadan discovered that the 6-year-old ban on him entering the United States had been lifted, he said the decision marked a new openness coming from America.

President Obama talked last summer about forging a “new beginning between the United States and Muslims around the world,” but many liberal critics have complained that he hasn’t stepped far enough away from Bush administration policies that have embroiled relations with the Islamic world.

But images of Mr. Ramadan traveling to at least six lectures across the US in the coming weeks may go a long way in advancing Mr. Obama’s goal of starting a new dialogue with the Muslim world. Ramadan is an Oxford professor who has been dubbed a “rock star” among many young European Muslims.

He was barred from coming to the US in 2004, first under a provision of the Patriot Act that allows the US to keep out anyone suspected of espousing ideas that support terrorism. While the government backed away from that initial reasoning, which kept him from taking a teaching job at the University of Notre Dame, it later said Ramadan contributed to an organization that funneled money to Hamas, the Palestinian group the US considers a terrorist organization.

Ramadan denied those allegations and said he never intended for any donation to reach Hamas. While he has been an outspoken critic of terrorism, he has also not been shy about speaking out against US policy.

“Many US organizations believe that I am being barred from the country not because of my actions but because of my ideas. The conclusion seems inescapable,” Ramadan wrote in a 2007 opinion piece for the Monitor.

“We do not think that either one of them represents a threat to the United States,” said Philip Crowley, a spokesman for the State Department, at a January press briefing. “We want to have the opportunity potentially to have Islamic scholars come to the United States and have dialogue with other faith communities and people here in our country.”

The Obama administration’s decision marks a shift from the Bush stance on visiting professors and other intellectuals whose ideas are often at odds with American policy, says Melissa Goodman, a staff attorney at the ACLU who worked on both the Ramadan and Habib cases.

“It’s an incredibly important first step to restoring a robust and free exchange of international ideas across borders,” she says.

Between 2004 and 2008, the ACLU received “a steady stream” of complaints about what it calls the “ideological exclusion” of academics, writers, and journalists. Now, Ms. Goodman says, several people once barred from the US are coming for the first time in years.

Ramadan said in a statement that his reentry “brings to an end a dark period in American politics that saw security considerations invoked to block critical debate through a policy of exclusion and baseless allegation.”

But many also say that Ramadan, whose grandfather founded the Muslim Brotherhood, should remain locked out of the country.

While many hail Ramadan as a preeminent Muslim thinker encouraging greater engagement between Islam and the West, others say that he is a radical whose extremist view of Islam is often masked by academic-speak.

"Tariq Ramadan's entry into America needs to be met with open dialogue from the Muslim Community, non-Muslim organizations, and the media on the real threat of Political Islam," said M. Zuhdi Jasser, AIFD president, in a statement. "It is incumbent on all Americans, especially American Muslims, to engage Ramadan at any opportunity to demonstrate that the US Constitution trumps the construct of the Islamic State."